Well, it might sound like a lot of money and a lot of steel, and a lot of penne a l'arrabiata, but it's the Galactic Empire, and it has the economic power of many worlds, not just one like the Earth, and some of these worlds might be many times the size of the Earth.
Is this based on NASA costs? Something tells me it would cost significantly less (just a few septillion?) if SpaceX would be making it.